1. Field of the Invention
The present invention relates to an antenna formed by a metal plate and a dielectric printed board and, more particularly, to a small-sized broadband antenna element and a method of using the same.
2. Description of the Related Art
In recent years, a TV reception antenna for digital terrestrial broadcasting and an antenna for a wireless TV using the UWB (Ultra Wide Band) technique require a very wide band.
For example, communications using the UWB technique is expected to use a frequency band of 3.1 GHz to 4.9 GHz.
There is a conventional broadband antenna having a structure as shown in FIG. 1. The antenna is disclosed in “plate antenna and television receiver having the antenna” of Japanese Patent Application Laid-Open No. 2005-203830 (document 1). A plate conductor 101 has a slit 102 on one side, and power is supplied through a coaxial cable 105.
Recent electronic devices such as a device having a USB interface have to be compact as typified by a USB (Universal Serial Bus) memory.
As a conventional technique related to miniaturization of an antenna, there is an antenna disclosed in “radio device” of Japanese Patent Application Laid-Open No. 2004-215132 (document 2).
The antenna disclosed in document 1 has a broadband characteristic but has a drawback of large dimensions. The dimensions are 210 mm×210 mm at the lowest useful frequency of 470 MHz, which are equivalent to “0.3 wavelength×0.3 wavelength”. The dimensions do not satisfy the demand for miniaturization of an electronic device.
The invention disclosed in document 2 relates to a so-called notch antenna which hardly covers a broad band. Further, since the circuit board itself is folded, it is difficult to reduce the thickness and the high manufacturing cost due to folding of the circuit board occurs.